Vacuum tube



E. G. MURPHY VACUUM TUBE Nov. 2o, 1934.

Filed Deo. 14, 1928 2 Sheets-Sheet l Z1/gaz A I jay/.4

NOV.y 20, 1934. E G MURPHY 1,981,115

VACUUM TUBE Filed Deo. 14, 1928 QSheets-Sheet 2 'nu .u

Patented Nov. 20, 1934 vUNITED STATES PATENT OFFICE 3 Claims.

This invention which relates to'vacuum tubes or electron dischargedevices is a continuation in part of and an improvement'over the subjecty matter of my copending application, Serial No. l 73,822, led December7, 1925, for Vacuum tubes and patented as Patent 1,699,011, Jan. 15,1929.

The main object of the invention is to provide an improved vacuum tubewith novel self-inclosed adjustable means whereby the tube may beoperated on those points of the locus of the characteristic curvesthereof that will result in maximum circuit eiliciency in radiotransmitting and receiving.

Another object is to provide a vacuum tube with adjustable insertablemeans for the variable control and regulation of the electrodes thereinindependently of external apparatus.

A further object is to provide a vacuum tube with self-inclosedadjustable means for varying the potential or bias to be applied to thegrid electrode of the tube.

More particular and special objects of the individual tubes and thevarious modifications herein disclosed will be set forth in separateparagraphs in the details hereinafter set forth, reference being had tothe accompanying drawings in which:

Figure 1 is a side elevation of a vacuum tube embodying my invention;

Fig. 2 is a vertical sectional view of Fig. 1;

Fig. 3 is a vertical sectional view of a slightly -modied form of thetube shown in Fig. 2, il-

lustrating the use of an insertable potentiometer for f'lne adjustmentof potential to one of the electrodes or for stabilizing the circuit;

Fig. 4 is a. diagrammatic view of the circuit embodied in the tube shownin Fig. 3;

f Fig. 5 is an enlarged longitudinal sectional view of one of theinsertable cartridge resistance units;

Fig. 6 is a modification of the form shown in Fig. 3;

Fig. 7 is a modified form of the invention showing the control of thegrid electrode by a combination cartridge condenser and grid leak;

` Fig. 8 is a modification of the form of the 'invention shown in Fig.2, with insertable means for varying the output impedance of the tube;

Fig. 9 is a combination tube showing adjustpedance of the tube, and axed value insertable cartridge resistance unit for the control of thelament;

1 ,Fig 10 is an enlarged longitudinal sectional view of a combinationcartridge condenser and able insertable means for varying the output im-(Cl. Z50-27.5)

grid leak employed in the tube illustrated in Fig. 7:

Fig. 11 is a transverse section taken on line 11-11 of Fig. 10;

. Fig. 12 is an enlarged longitudinal sectional view of a fixed valuecartridge resistance unit employed in the tube illustrated in Fig. 9;

Fig. 13is an elevational View of the exterior ofA a modified form oftube showing an enlarged base for the reception of heavy duty cartridgeunits; and

Fig. 14 is a longitudinal sectional view of a cartridge potentiometerunit as employed in the tubes shown in Figs. 3, 4 and 6.

In the drawings wherein similar characters of reference indicatecorresponding parts in the several views of the preferred forms of myinvention, A designates a glass envelope secured to a base B having asubsocket 15 to be described more fully elsewhere in the presentspecification. Formed integrally with the envelope is the press 16 inwhich are imbedded the supporting rod 17 for the cathode 18, the rod 19for the grid 20, and the rod 21 supporting the anode or plate 22.

In the construction shown in Figs. 1 and 2, one of the electrodes, inthis instance the filament, is variably controlled by the insertablecartridge resistance unit C which is clampingly held in the socketmembers 23, 24 which are formed of short sections of split metal tubingcrimped to opposite sides of the wall of the base.

To the bottom of the base B of the tube are secured thecircuit-completing prongs which include the filament prongs 25, 26; thegrid prong 27 which is connected to the grid electrode by wire 28, andthe anode prong 29 which is connected to the anode by lead 30. Byinspection of Fig. 2, it will be seen that filament prong 26 isconnected by wire 31 to right hand socket member 24 whence the filamentcircuit may be completed through the cartridge element C which may beslid transversely of the arm 32 secured on the inner bottom of the baseof the tube, the arm contacting with resistance winding 33, whereby theresistance and consequently the current fed to the filament 18 via lead34 attached to arm 32, may be varied.

The resistance cartridge unit C which is employed in the tube shown inFigs. 1 and 2, is shown in detail in Fig. 5. It consists of a tube 35 ofglass or other suitable insulating material closed at each end by caps36, 37 containing p1ugs of fusible metal as, 39 connected ,1-

:may be of any suitable ohmic resistance.

conventional capacity by merely thrusting La short section of metal rodof suitable size into the subsocket 15 in place of cartridge unit C. Theprovision of a fuse in the cartridge element C is particularly valuablein the case of power and transmitting tubes wherein the' destruction ofthe lament is a costly matter as the tube is thereby in most casesrendered worthless. The

filament circuit of the tube shown in Figs. 1 and 2 is energized fromprong 25, wire 25', rod 17, filament ,18, lead 34, arm .3.2, windingV33, cap 36, metal plug 38, fuse 40, metal plug 39, metal cap 37, socketmember 24, wire 3l and prong .26 to battery D or other source of.electrical energy.

In the modification shown in Fig. 3, the circuit of which is shown inFig. 4, the filament circuit is shunted :by an insertable .potentiometerunit in the form of the cartridge E, the winding of which maybevconnected to the plate or grid electrodes through the arm 32. Thepotentiometer E is shown in detail in Fig. 14

' .and comprises a section of `dielectric tubing 41 closed at each endby caps 42, 43 connected by the exterior `inductive winding' 44 whichlatter In this respect, I have found the use of nichrome wire inpractice to offer certain advantages `as a winding for the potentiometersince its resistance is high .enough to permit the use of acomparatively few .turns of wire in order to obtain the desiredresistance value. A fifth `prong 45 in the tube illustrated in Fig. 3,may be outwardly connected .to the positive or negative of vthe sourceAof plate energization, in this manner .a fine adjustment of thefilament-plate potential may be obtained.. This feature is especiallydesirable in thermionic detectors and particularly so in soft or gaseousthermionic valves which are exceedingly sensitive and responsive toslight Variations of potential. It will be apparent from inspection .ofFig. 4 that the grid return can .be applied to the positive or negativeside of the filament battery and that consequently the vgrid `bias canbe graduated nely between positive and negative values. In Fig. 4,.byway of eX.- ample, both the plate vand the grid are connected to thepotentiometer, but it will be obvious .that either Vthe grid returnsingly or the plate return singly may be Vapplied to the positive or`negative side of the filament battery or other Lsource of power throughone of the prongs 25,

26,-if desired. The lament circuit of the tube shown in Fig. 3, anddiagrammatically shown in Fig. 4, is completed from the prong 25, wire25,-rod 17, `filament 18,V lead 34 to prong.26,- wire 25 and lead 34being also `connected to socket members 23,24 between which thepotentiometer E is secured,-,-this potentiometer as illustrateddiaerammatically in Fig. 4 .permitting or shunting a part of thefilament current vto iiow through the winding 44 which in this instance.as indicated above, may be of compara- Should the fuse melt, thusbreaking .description as that shown in Fig. 3 except that the fifthprong has been eliminated and a binding post 46 substituted,the wiringconnections Vin .the `interior of the base otherwise being identicallythe same. Where it is not desired to -employ five -prong tubes, thisform offers an alternative.

In Fig. 7, a combination cartridge grid leak and condenser F is shownwhich is inserted between the vsocket members 23 and 24 in series withthe grid electrode ofthe tube which may be of the usual conventional`structure -so far as the disposition of the envelope, press andelectrodes is concerned. The `element, F, as shown in Fig. 10, comprisesa tube of dielectric 47 having an inner coating 48 of high resistancemetal serving as an electrode grid leak. 'Ihe leak resistance 48 mayeither be sputtered .on the inner Wall of the glass tube 47, .or itmaybe east With the glass .as one of the ingredients of the latten-anumber of metallic salts in suitable proportion with the other wellknown ingredients of glass answering the purpose indicated. A metal plug49 of fusible metal closing one end of the tube is connected vtothe'ends of a number of separated sheets of metal or foil 50 insulated,one from the other b y sheets of paraffmed paper 51, -these sheets ofmetal being t separated by the paper sheets from other sheets or metalor foil 52 thelatterbeing attached to the .opposite metal plug 53. Themetal plugs 49 and 53 are in con-tact with the electron leak resistance48 which is chosen `of .suitable value and preferably between the usuallimits of ,105

and l0rl ohms. Metal caps 54 and 55 at either end of the tubing 47complete this combination grid leak and condenser which Aas a cartridgemay be inserted in the subsocket 15 .of the tube shown in Fig. 7. Thegrid circuit may now be energized frornprong '27, lead 28', socketmember 24, cap 55, metal plug 53, through leak resistance 48 andelectrostatically through the sheets 50 and 52 of the condenser element,metal plug l49, cap 54, socket member 23, to lead 28 and grid 20.

Fig. 8 in .its construction, is based substantially on `the form of tubeshown in Figs. 1 and 2,--

the cartridge unit C in this modification being inserted in the:subsocket l5 in series with the plate electrode 22 whereby the plate oroutput impedance of the .tube may be equalized with .the loadresistance. As is well known to those skilled in this art, thepoweroutput ,of a thermionic valve is greatest when the plate impedance`of the tube or valve Ais madesubstantially `equal'to the loadresistance.. noted that in all forms of receiving sets employing vacuumtubes, and particularly thoseL:4

It is also to be circuits employing high frequency oscillationtransformers the electrical constants `of which are of uniform value,the use of thermionic valves of vsubstantially .the :same outputimpedance is nimperative if the maximum possibilities or eiiiciency ofthe circuit is to be realized. As indicated in Fig. 8, the plateimpedance of a series of thermionic valves can be matched, one with theother, assuming the tubes to be of the same type and average capacity.The cir- I cuit of this tube, as illustrated in Fig. 8, so far as theplate circuit is concerned, is completed from prong 29 to clampingsocket member 24, cap 37, metal plug 39, resistance strip 40, metal plug38, cap 36, winding 33, arm 32, lead 22 to anode 22.

Fig. 9 shows a modication embodying a combination of means forcontrolling the output impedance of the tube and for regulating thefilament circuit. The plate circuit of this tube is completed from anodeplate 22, wire 32 to socket member 56, cap 37, metal plug 39, resistancestrip 40, metal plug 38, metal cap 36, winding 33 and contact arm 57 toprong 29. The means for regulating the filament circuit comprises a xedvalue resistance unit G, shown in Fig. 12, which is placed in serieswith the filament. The unit G consists of a section of dielectric tubing58, closed by metal caps 59, 60 which inclose plugs of fusible metal 61,62 in which are imbedded the ends of the winding 63 which, in thismodification is within the interior of the tubing 58. When the cartridgeunit G is placed in the socket members 23, 24, the filament circuit maynow be completed from prong 26, socket member 24, cap 60 of element G,metal plug 62, winding 63, metal plug 6l, cap 59, lead 64, filament 18,rod 17, wire 25' to prong 25.

In Fig. 13, a tube is shown wherein the base is enlarged to accommodatecomparatively large or heavy-duty cartridge units. The prongs and theimmediate lower part of the adjoining bottom of the base of this tube,however, is of conventional construction so that it may be received byany of the standard tube sockets.

If alternating current is employed to energize the lament and platecircuits of these tubes, the modification shown in Fig. 3 isparticularly desirable as the objectionable hum especially noticeable inlow-voltage alternating current circuits when connected to soundreproducing means-can be almost completely eliminated. This isaccomplished by inserting a cartridge resistance element E in thesubsocket 15 and then applying a positive potential from the plateenergizing source. In this instance, it is assumed that a separateinsulated cathode of conventional type is employed in addition to theheating lament. The grid bias in the alternating current type ofthermionic valves is, of course, obtained from the alternating currentplate current supply by inserting a cartridge resistance of suitablevalue between the negative pole and positive pole of the filamentenergizing source and then connecting the grid and plate electrodes asshown in Fig. 4. The correct value of the resistance required is deducedfrom the IR drop across this resistance, the grid bias required beingknown from the characteristics of the particular tube, assuming definiteplate potentials.

It will be apparent from the foregoing description and illustrationsthat the invention lends itself to the widest modification and change,and it is accordingly to be understood that the types described aremerely representative; hence, I do not coniine myself to the detailsprecisely as set forth but desire to avail myself of such variations andembodiments as fairly fall within the limits of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

l. In combination, an electron discharge device having lament, grid andplate electrodes in an envelope, a base secured to said envelope andmeans removably insertable in the base including a manually adjustablecartridge potentiometer element electrically connected to the ends ofone of said electrodes and to at least one other of said electrodes,whereby when said potentiometer element is moved relatively to a contactconnected to one of the electrodes, the filament-plate potential may bevaried and simultaneously therewith a variable positive and negativepotential selectively applied to the grid electrode.

2. An electron discharge device suitable for alternating currentenergization comprising an envelope having a plurality of electrodesmounted therein, a base secured to said envelope, circuit completingprongs attached to the base, and means insertable in said base formaking operative the electron discharge device, said means including acartridge inductance movable transversely of a contact member securedwithin the base and electrically connected to at least one of theelectrodes, for negatively and positively biasing, optionally as desiredone of the electrodes and varying the potential gradient along anotherof said electrodes, said prongs being electrically connected to saidelectrodes.

3. In combination, an electron-discharge device having a plurality ofelectrodes fastened in an envelope directly secured to mechanical means,an arm secured to said means, a tubular potentiometer slidablyengageable with said arm, a pair of clamping memberselectricallyconnected to at least one of the electrodes and operative to receivesaid potentiometer Within the said means, and external means forelectrically connecting the arm to the potentiometer and thereby to atleast one of the said electrodes for optionally applying and carrying apositive and negative potential to another of said electrodes.

EDMUND GUYER MURPHY.

